- Move "gclient bootstrap" out of engine/README.md into a section in the
"Setting up the Engine development environment" doc.
- In the "gclient bootstrap" section, instruct Googlers to follow the
RBE setup docs.
- Update the "Additional Steps for Web Engine" to reflect the fact that
the user's gclient file is copied from a template that contains a
commented-out web engine entry.
- Link to the "Engine Tool" docs instead of to "Compiling the engine"
for the next steps.
- In the RBE doc:
- Update the gclient instructions to reflect that the gclient file may
be copied from rbe.gclient.
- Move the "gcloud" section into the "Getting started" parent section.
The gcloud setup is required before any of the next steps.
- Instead of suggested the "gcloud auth application-default login"
command in case of an error, directly instruct the user to run this
command. It's required for things to work.
- Add a "Too many open files" section to the Troubleshooting parent
section.

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